This invention relates to an electro-optical device such as a display device, a shutter array for printers, a shutter for camera or an optical shutter for window, using a ferroelectric liquid crystal having a ferroelectric property. More particularly, the present invention relates to an improvement in an alignment treatment which controls the arrangement of liquid crystal molecules.
Conventionally, electro-optical devices produced by sandwiching a ferroelectric chiral smectic liquid crystal between two substrates have been known in the past.
Such a ferroelectric liquid crystal device is described in U.S. Pat. Nos. 4,367,924 and 4,563,059 (Clark et al.).
We have filed the related application (Ser. No. 750,092) with respect to a ferro-electric liquid crystal electro-optical device in which alignment treatment having uniaxial alignment characteristic is applied to one of the substrates and random alignment treatment having non-alignment characteristic is applied to the other substrate, in order to rearrange the liquid crystal molecules in a bi-stable state. In other words, the liquid crystal molecules that are arranged in one stable state are rearranged in the other stable state by applying a voltage in order to utilize the optical change occurring thereby.
However, the conventional ferroelectric chiral smectic liquid crystal electro-optical devices involve the following problems.
First of all, no suitable material which provides random alignment to the liquid crystal molecules has been found. Since physical properties to be satisfied by a preferred material are not clarified, the selection of the material must be made by the method of trial and error. In addition, it has not been possible by use of the conventional random alignment materials to establish a clear and stable bi-stable state of the liquid crystal molecules. As a result, the light transmission cutoff contrast resulting from the change-over of the alignment state of the liquid crystal molecules in the bi-stable state by the application of a voltage is not sufficiently high.